U.S. Secretary of State John Kerry (C) leaves the Intercontinental Hotel in Geneva September 12, 2013, before his meeting with Russian Foreign Minister Sergei Lavrov. Credit: Reuters

U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov opened talks on Thursday on disarming Syria's chemical weapons programs, but differences emerged at the outset of the expected two-day negotiations.

Kerry reiterated the U.S. position that military force might be needed against Syria if diplomacy over President Bashar al-Assad's chemical weapons stockpile fails.

"President (Barack) Obama has made clear that should diplomacy fail force might be necessary to deter and degrade Assad's capacity to deliver these weapons," Kerry said, as Lavrov looked on.

But Lavrov made it clear that Russia wants the United States to set aside its military threats for now.

"We proceed from the fact that the solution of this problem will make unnecessary any strike on the Syrian Arab Republic," he said. "I am convinced that our American colleagues, as President Obama stated, are firmly convinced that we should follow peaceful way of resolution of conflict in Syria."

As the U.S. Congress debated military strikes as a response to an August 21 chemical attack on a suburb of Damascus, Russia proposed that Syria instead agree to give up its chemical arms.

Kerry made clear that Washington, while exploring the offer, remains skeptical. And he pushed back on a reported offer from the Syrian government, as part of a move to join the Chemical Weapons Convention, to supply data on its chemical arsenal within 30 days, the standard practice.

"We believe there is nothing standard about this process at this moment because of the way the regime has behaved, not only the existence of these weapons but they have been used," Kerry said.

"Expectations are high. They are high for the United States, perhaps even more so for Russia, to deliver on the promise of this moment," Kerry said. "This is not a game and I said that to my friend Sergei when we talked about it initially. It has to be real. It has to be comprehensive. It has to be verifiable. It has to be credible. It has to be timely and implemented in a timely fashion, and finally there ought to be consequences if it doesn't take place."